>>>In some cases null is a must. Consider a lab result, where null means "was not done", and zero means "done, none found".
>
>I see the theorectical basis for it Dragan, but usually, I'd reply on a positive indicator in another column to tell me whether or not a lab test had been done, or perhaps there might be no row in the table at all if it hadn't been done.
>To my pedestrian brain It's like saying that a NULL date of birth in a kid's record means that the kid was never born.
>If he was never born then there's no kid!

Or the guy's birth records burned with the church when Napoleon invaded the area, and he's too old remember? There were such cases. A null simply means "no datum" (a singular of data).